The present invention relates to pumping devices, related equipment and methods and more particularly to inverted peristaltic pumps, tubing kits for use with such pumps and related methods for using such pumps.
Numerous types of peristaltic pumps have been known in the prior art. In general, peristaltic pumps are devices that transfer fluid through one or more elongate, at least partially flexible, tube(s) by compressing each tube in a peristaltic manner. Such peristaltic compression of the tube serves to push or pull fluid through the lumen of each tube. The fluid transport is effectuated by moving the region of compression along the length of the tube. Such movement of the region of compression is typically achieved by way of one or more rollers driven by a mechanical drive mechanism that guides each roller along a re-circulating path. The path of each roller is typically configured such that each roller will pinch-off the inner lumen of the tube it moves along a portion of the length of the tube. Most commonly the roller rotates in a circular path about a central axis of rotation.
In order for a peristaltic pump to function as a positive displacement pump, it must effect at least first and second regions of compression on each tube and the second region of compression must be created before the fist region of compression is released. The length of the tube between the first and second regions of compression define a period.
Typically, the each peristaltic pump tube is mounted within the in a U-shaped or arc-shaped configuration whereby some portion of each tube overlaps a potion of a path traveled by a roller. In some peristaltic pumps, the desired compression or pinching-off of each tube is achieved by compressing the pump tube(s) between the roller(s) and an adjacent stationary member (a backing plate). In other peristaltic pumps, the desired compression or pinching-off of the tube(s) is achieved by stretching the tubes over the roller(s), without involvement of any stationarily member or backing plate, however such designs can be somewhat disadvantageous due to the propensity for most plastic tubes to stretch or creep thereby resulting in loosening of the tube(s) over time.
One advantageous feature of virtually all peristaltic pumps is that the fluid does not contact the pump""s mechanical drive mechanism since the fluid is always confined within and moved through the flexible tube(s). Therefore, by using the peristaltic pumps for a medical application, the cost of the disposable or re-sterilizable portion of the medical instrument may be reduced.
One drawback associated with at least some peristaltic pumps is that the fluid outflow from a peristaltic pump tends pulsate. The prior art has included devices and methods that purport to reduce such pulsation, such as the reduced pulsation pump head described in U.S. Pat. No. 5,230,614 which has multiple rollers that compress the tube at relatively close intervals, thereby minimizing the pulsatile nature of the pump outflow. This method of fluid transfer may be costly and the wear and tear on the tubing can be high. Since each roller is collapsing a small portion of the tube at any given time, the likelihood of the tube to creep or become displaced is high.
Other prior art patents describe other modification to the traditional peristaltic pump designs including the use of a helical tubing arrangement as described in Canadian Patent No. 320,994, a multiple tube and cylindrical format as described in U.S. Pat. No. 5,688,112, a looped tube path as described in U.S. Pat. No. 5,630,711 and a single roller loop tube as described in U.S. Pat. No. 5,429,486.
The loading of the pump tubing on common peristaltic pumps is often cumbersome due to the fact that the flexible tubes are typically unsupported until loaded, and this my not be easy to maneuver into place.
The present invention overcomes at least some of the shortcomings of the prior art peristaltic pumps by providing peristaltic pumps that provide relatively non-pulsatile flow with tubing that is easily loadable and may be pre-mounted on a central core member.
The present invention provides new peristaltic pump devices in which the tube(s) is/are mounted on an arched or round central core member and one or more compression members (e.g., rollers, feet, a cylinder, etc.)) rotate, circulate, traverse or otherwise move about the central core member so as to cause the desired regions of compression in the pump tube(s). This arrangement results in comparatively smooth, non-pulsatile fluid transfer. Also, this arrangement allows for perpendicular rather than tangential compression of the tube(s), thereby minimizing the potential for creeping of the tube(s). In the peristaltic pumps of the present invention, the central core member may be stationary and the compression member(s) (e.g., rollers, feet, a cylinder, etc.) may rotate about the stationary core member. In pumps of the present invention, the tub(s) may be formed or mounted on a reusable or disposable core member to form a unitary tubing/core member assembly that is insertable as a unit or cartridge into the pump, thereby eliminating leakage as tubing is replaced and resultant potential for contamination of the pump components and/or the user""s body. Also, in pumps of the present invention, the central core member (e.g, central backing plate) may provides an effective means to maintain or change the temperature of fluid being pumped through the pump tube(s) and, thus, may incorporate or include a heating or cooling element.
In accordance with the present invention, there are provided peristaltic pumps that are of an inverted design (i.e., wherein the fluid conduit (e.g., tubing) is mounted on a central core and a compression member revolves at least part way around the central core to compress the fluid conduit, thereby propelling fluid through the fluid conduit and methods of pumping fluids using such pumps. The inverted peristaltic pumps of the present invention provide economical and controlled fluid delivery with low pulsation and have applicability in many medical and non-medical applications.
Further in accordance with the present invention, the compressible fluid conduit (e.g., tubing) may be mounted or formed on the central core such that it is in abutting contact with the outer surface of the central core, thereby maintaining the desired size and shape of the fluid conduit with minimal stretching or deformation of the fluid conduit during use. Also, changing of the fluid conduit or tubing is simplified by the present invention because the central core having the compressible fluid conduit (e.g., tubing) pre-mounted or pre-formed thereon may be simply inserted into the pump in a position whereby the compression member will rotate at least partially around the core, thereby causing peristaltic compression of the fluid conduit (e.g., tubing) against the central core. Also, the central core may be provided with heating or cooling elements so as to heat or cool fluid as it passes through the fluid conduit(s) mounted or formed on the central core.
Still further in accordance with the present invention, in at least some embodiments, one or more grooves may be formed in the outer surface of the central core and the fluid conduit (e.g., tubing) may be mounted or formed within such groove(s). In some embodiments, a single helical groove may be formed in the outer surface of the core and the fluid conduit (e.g., tubing) may be mounted or formed within such helical groove. In many embodiments, it will be desirable for the fluid conduit (e.g., tubing) to make at least one full rotation around the central core. As described more fully herebelow, in some embodiments wherein the fluid conduit (e.g., tubing) is mounted or formed within groove(s), the depth of such groove(s) may vary to facilitate gradual increasing and decreasing of the amount of compression being applied to the fluid conduit as the compression member moves about the central core. In this regard, the ends of the groove(s) may be deeper than the center of the groove(s) so as to provide for gradual compression of the fluid conduit (e.g., tubing) from one end of the groove where the lumen of the fluid conduit is fully open to a point of complete compression (i.e., where the lumen of the fluid conduit is completely pinched off) followed by gradual decompression to the other end of the groove where the lumen of the fluid conduit is once again fully open.
These general aspects of the invention, as well as numerous other aspects and advantages of the invention, will become apparent to persons of skill in the art who read and understand the following detailed description and the accompanying drawings.